A new type of high effective complex coagulant polysilicate aluminum ferric (PSAF) was prepared from fly ash and pyrite slag. The results showed that PSAF had a good coagulation effect in the pre-treatment of abermectin wastewater. The optimum conditions were that the pH value of influent was 6.5～7.5, the dosage of PSAF was 80mg/L, the concentration of COD,SS and ρ(AVM)''s removal rate reached 18.9%,34.6% and 20.5%, respectively. The effluent BOD₅/COD of abermectin wastewater was increased from 0.31to 0.42, and the biodegradability was improved a lot.